2.9 KiB
JKQtPlotter
Plotting Parametric Curves
This project (see ./examples/simpletest_parametriccurve/) demonstrates how to draw parametric curves, using [JKQTPxyLineGraph}(https://github.com/jkriege2/JKQtPlotter/tree/master/examples/simpletest) and JKQTPxyParametrizedScatterGraph.
The source code of the main application can be found in jkqtplotter_simpletest_parametriccurve.cpp. First, the parametric curve (here a logarithic spiral) is sampled into two columns containing the x- and y-values along the curve. In addition the radial distance from x=y=0 is added into a third column:
QVector<double> X, Y, R;
const int Ndata=500; // number of plot points in each curve
const double phiMax=4.0*M_PI;
const double a=1;
const double k=0.2;
for (double phi=-phiMax; phi<=phiMax; phi+=phiMax/double(Ndata)) {
const double x=a*exp(k*phi)*cos(phi);
const double y=a*exp(k*phi)*sin(phi);
X<<x;
Y<<y;
R<<sqrt(x*x+y*y);
}
// and copy it to the datastore
size_t columnX=ds->addCopiedColumn(X, "x");
size_t columnY=ds->addCopiedColumn(Y, "y");
size_t columnR=ds->addCopiedColumn(R, "r");
Then simples graph just uses the columns X and Y to plot the curve:
JKQTPxyLineGraph* graph1=new JKQTPxyLineGraph(&plot);
graph1->set_xColumn(columnX);
graph1->set_yColumn(columnY);
graph1->set_drawLine(true);
graph1->set_symbol(JKQTPnoSymbol);
graph1->set_title("one-colored spiral");
plot.addGraph(graph1);
If you use JKQTPxyParametrizedScatterGraph instead of JKQTPxyLineGraph, you can also modify the color of the line-segments, connecting the datapoints:
JKQTPxyParametrizedScatterGraph* graph2=new JKQTPxyParametrizedScatterGraph(&plot2);
graph2->set_xColumn(columnX);
graph2->set_yColumn(columnY);
graph2->set_colorColumn(columnR);
graph2->set_palette(JKQTPMathImageMATLAB);
graph2->set_symbol(JKQTPnoSymbol);
graph2->set_drawLine(true);
graph2->set_title("colored spiral");
graph2->get_colorBarRightAxis()->set_axisLabel("color scale radius $r(\\phi)$");
plot2.addGraph(graph2);
The result looks like this:
... and with the line-color set by the radius:
